2000 Buick LeSabre dies while driving - still

My girlfriend's car has been dieing on her for a few
months now. First the mechanic thought it was the
ignition switch. Then we fixed oil/coolant/co2
leaks. Next was the battery. Today we replaced the
crank shaft position sensor and MAF sensor. And it
still died on the way home from the mechanic. It
does at idle and while driving. It used to happen
once a week or so, now it happens every day. The
car always starts right back up. The battery light
comes on when it dies, but then goes off when
restarted. The enigine light is off. The mechanics
said even when it died on them in the shop, the car
did not give any error codes. Has anyone
experienced a similar problem, or have any
additional suggestions? We are frustrated and at
the end of our rope. The car has almost 200,000
miles.